Oxidation resistant lubricant



United States Patent 3,135,692 GmATiGN RESlSTANT LUBRHEANT Manley Kjonaas, Hammond, Ind, assignor, by mesne as= signrnents, to Sinclair Research inc, New York, N.Y., a corporation oi Delaware No Drawing. Filed May 21, E56, Ser. No. 585,981 7 Claims. (Cl. 252-32.7)

The present invention relates to mineral oil ompositions and more particularly to the use of novel additives to impart anti-oxidant and detergent properties to lubricating oils.

Various detergent additives have heretofore been proposed for use in mineral oil compositions, such as heavy duty lubricating oils, which are suitable for use as crankcase lubricants for internal combustion engines, including automobile, diesel and marine engines, which operate for long periods of time at high temperatures and in which the lubricant comes in contact with metal surfaces. In general, the function of these detergent or dispersant type additives is to impart properties to the motor oil which will enable it to 'keep the pistons, ring and valves free of varnish and lacquer deposits by keeping oil oxidation products and other types of insoluble matter in suspension so that these materials will not settle out and adhere to metal surfaces. The metal derivatives of organic compounds, such as substituted phenols and sulfonic acids, are among the most Widely used additive agents to improve the detergent properties of a lubricating oil. However, While these detergent additives perform satisfactorily in dispersing sludge and preventing lacquer deposits, many of these additives, particularly under extreme operating conditions, increase the rate of oxidation of the oil and effect increased concentrations of acidic oxidation products which thus increase the rate of corrosion to the bearings, pistons, valves and the like.

in accordance with my invention, I have discovered new and useful detergent-anti-oxidant additives prepared by reacting an oil-soluble basic barium phenol sulfide with an oil-soluble material selected from the group consisting of petroleum sulfonic acids, dithiophosphoric acid diesters, and phosphorus sulfide-hydrocarbon reaction products. I have found that these combinations of constituents produce detergent materials having particularly desirable properties for use in lubricating oils, including sludge dispersant properties, anti-Wear properties and the prevention of varnish formation and lacquer-like deposits. The useful additives of my invention provide lubricating oil compositions with improved resistance to oxidative deterioration whereby the corrosion to valves, bearings, pistons and the like, is reduced rather than accelerated.

The novel detergent-antioxidant lubricating oil additives of this invention can be employed in amounts varying over a considerable range depending upon the intended purpose of the resultant composition and the conditions under which it is to be used. In compositions intended for use as crankcase lubricants for internal combustion engines, the amount of additive employed based on the total weight of the mineral oil composition, may range from 0.01 to 25.0 weight percent, preferably is from about 0.5 to, 10.0 weight percent. In addition, the lubricant composition advantageously may contain from about 0.001 to Weight percent of anti-wear agents and anti-oxidants such as ele mental sulfur, zinc dithiophosphate or other organic sulfur compounds, such as sulfurized sperm oil and the like.

Furthermore, the lubricant may contain other agents such as dyes, pour depressors, thickeners, viscosity index improvers and any of the agents conventionally used as additives for lubricating oils.

In carrying out the preparation of the additives of this invention, it is preferred to use ratios of the phosphorus sulfide-hydrocarbon, sulfonic acid or dithiophosphoric acid diester materials which would theoretically neutralize one-half of the total barium content in the basic barium phenol sulfide so as to obtain products which are substantially basic to pH 4. However, if a neutral oil blend is desired, then chemically equivalent quantities of the reactants can be employed.

The reaction between the basic barium phenol sulfide and the material selected from the group consisting of petroleum sulfonic acids, dithiophosphoric acid diesters and phosphorus sulfide-hydrocarbon reaction products is carried out by mixing the desired materials at a temperature from about room temperature to 500 F. or more, preferably about to 200 PI, until the reaction is complete. Ordinarily, after about one hour the reaction is considered complete, although after reacting at lower temperatures, eg to F. the product can be heated to about 250 to 309 F. to remove the water of reaction. Although my new additives are described as reaction products, I do not wish to be bound by theory as there may in fact not be a reaction effected.

The basic barium phenol sulfides which can be reacted with the material selected from the group consisting of petroleum sulfonic acids, dithiophosphoric acid diesters and phosphorus sulfide-hydrocarbon reaction products, include the oil-soluble basic barium salts of alkyl phenol sulfides, for instance, those in which the total number of carbon atoms in the alkyl group or alkyl groups is about 8 to 24, such as dodecyl, n-decyl, cetyl, and the like. Suitable alkyl phenol sulfides which may be employed are tertiary-octyl phenol sulfide, 2,4-diamyl phenol sulfide, 2-ethylhexyl phenol sulfide, (I -C branched chain alkyl phenol sulfides and the like.

In the preparation of the basic barium salts of the above-mentioned phenol sulfides the phenol radical is neutralized with a sufficient amount of a basic barium compound so as to obtain an oil-soluble basic salt which contains at least about 1.2 times the theoretical amount of metal required to form the normal barium salt. This reaction can be brought about by heating the metallic oxide or hydroxide directly with the phenol in the presence of a suitable solvent under conditions well known in the art.

The phosphorus sulfide-hydrocarbon materials which are employed in the present invention to produce the novel lubricating oil additives are the oil-soluble reaction products of a sulfide of phosphorus with a suitable hydrocarbon material of lubricating viscosity, such as a material of natural petroleum origin, for example, a heavy hydrocarbon oil of lubricating viscosity having a molecular weight above 500, Le, residual lubricating oils, or a synthetic hydrocarbon material such as an olefin or olefin polymer having a molecular Weight of from about 400 to 2000 or more. In carrying out the phosphorus sulfidehydrocarbon reaction, the hydrocarbon material can be reacted with from about 1 to 50 Weight percent, and preferably 5 percent to 25 percent of a sulfide of phosphorus, such as P 5 P 8 P 8 or mixtures thereof, at a temperature of from about 200 to 500 F. in a non-oxidizing atmosphere such as an atmosphere of nitrogen. The final reaction product will usually contain from about 1 to 6 percent by weight of organically combined phosphorus.

In a preferred embodiment, a hydrocarbon material such as a mineral oil bright stock or cylinder stock having a viscosity within a range of about 120 to 300 SUS at 210 F. is reacted with 7 to 17 weight percent of phosphorus pentasulfide at a temperature between about 400 to 500 F. for a period of about 1-0 to 20 hours. By reacting a phosphorus sulfide with a bright stock, for example, the formation of oil-soluble products which are pro-sludging in typical lubricating oil blends are greatly reduced as compared to the reaction with a lighter oil, such as a neutral oil, which affords a larger percentage of insoluble reaction products. Ordinarily if the reaction mixture contains insoluble products these materials can be removed by filtration or centrifugation performed at an elevated temperature, usually about 150 to 280 F. Advantageously, the final reaction product may be steam-treated until only trace amounts of hydrogen sulfide are evolved. Other suitable hydrocarbons which can be reacted with phosphorus sulfide include olefins such as cetene, melene, high molecular weight alkenes obtained by cracking petroleum oils, etc. and olefin polymers such as those obtained in the liquid phase polymerization of butylene, and isobutylene in the presence of a Friedel-Craftstype catalyst.

The dithiophosphoric acid diesters which can be reacted with basic barium phenol sulfide to obtain the new composition of this invention are oil-soluble and include a wide variety of acid esters conventionally prepared by reacting a sulfide of phosphorus, preferably phosphorus pentasulfide, with a phenol, alcohol or mercaptan, under conditions of esterifieation well known in the art. The organic group in the acid diesters may be a straight chain, branched chain, aryl or cycloaliphatic hydrocarbon group which may or may not have other substituent groups such as sulfur, halogen or nitro groups attached thereto. Suitable alcohols used in the preparation of diester dithiophosphoric acids'contain from 6 to 18 carbon atoms and include such alcohols as hexyl, heptyl, 2-ethyl amyl, octyl, iso-octyl, 2-propyl amyl, decyl, undecyl, dodecyl, hexadecyl, 2-ethy1 hexyl, methylisobutylcarbinol, cyclohexanol, methyl cyclohexanol, or a mixture of C primary and C secondary alcohols, etc. Suitable phenols which may be employed are the alkylated phenols such as octyl cresol, p-octyl phenol, p-tertiary amyl phenol, tertiary butyl cresol, dodecyl phenol and the like. Similarly, if a higher sulfur content of the acid ester is desired, then the corresponding mercaptan of the abovedescribed materials can be employed. In general, the esterification reaction is carried out by reacting the desired alcohol, mixture of alcohols, phenol, or mercaptan with phosphorus pentasulfide at a temperature of about 120 to 350 F. until esterification is complete.

Suitable sulfonic acids which may be employed in accordance with the present invention are the oil-soluble sulfonic acids and particularly the sulfonic acids produced in the treatment of petroleum hydrocarbons with a sulfonating agent such as sulfuric acid or sulfur trioxide. The preferentially oil-soluble sulfonic acids, generally referred to as mahogany acids, are conveniently employed as a concentrate in the oil from which they are derived and may be prepared by sulfonating a suitable petroleum distillate with fuming sulfuric acid to obtain approximately a weight percent concentration of mahogany acids in the acid oil, or by sulfonating with sulfur trioxide in which case approximately a 20 weight percent concentration is obtained. The useful mahogany acids generally have a molecular weight of 300 to 500 or higher.

The base mineral oil used in the preparation of the lubricating composition will ordinarily depend upon the Example I PREPARATION OF ACID OIL A 270 SUS at 100 F. viscosity Sweet West Texas gas oil fraction was treated with four 28 pound per barrel dumps of 20% oleum. The sludge was removed after each oleum dump. The acid-treated oil was freed of, S0 by air blowing to leave a solution of approximately 10% mahogany sulfonic acid in oil which had an acid No. of 14.1.

Example II PREPARATION OF DITHIOPHOSPORIC ACID DIESTER.

Four moles (based on hydroxyl value) of mixed C and C alcohols were reacted with 1 mol of P 8 at 160- 170 F. to give a dithiophosphoric acid ester which analyzed as follows:

Percent sulfur 19.2 Percent phosphorus 9.72 Acid No. 155.8.

Example III PREPARATION OF PzSs-HYDROCAR-BON PRODUCT 1106 gallons of a SUS at 210 F. viscosity Mid- Continent bright stock was charged to the reaction kettle and heated to 275 F. 1200 pounds of P 8 was added while stirring and the temperature was brought up to 440 F. for 14 hours. The reaction mixture was cooled to 275 F. and filtered with Super-Cel to leave a product which analyzed as follows:

Percent sulfur 5.78 Percent phosphorus 3.13 Acid No 32.7

Example IV PREPARATION OF STEAMED PzSs-HYDROCARBON PRODUCT 1000 gallons of oil-P 8 reaction product concentrate, as prepared in Example III, was charged to the reaction kettle and heated to 285 F. Steam was passed through the reaction mixture for 8 hours with the temperature at 300325 F. After the steaming was completed the temperature was held at 300 F. for 15 minutes to dehydrate the product. Super-Cel was added and the product was filtered. It analyzed as follows:

Percent sulfur 1.55 Percent phosphorus 3.04 AcidNo. 68.7

Example V PREPARATION OF BASIC BARIUM PHENOL SULFIDE CONCENTRATE 6309 grams of octyl phenol was placed in a 22 liter three neck flask. 6309 grams of toluene was added and the mixture was stirred until complete solution was attained. Stirring was continued while 2670 grams of SO1 was slowly added during a 6 hour period of 75-135 F. The mixture was then heated at reflux (about 240 F.) for 6 hours. The toluene was topped out by heating the mixture to 300 F. Dry nitrogen was bubbled through the product until toluene distillation ceased. 3000 grams of this product was dissolved in 6000 grams of a 200 SUS 'at 100 F. viscosity 95 VI solvent treated Mid-continent neutral. 4000 grams of water and 3000 grams of barium oxide were added. The mixture was diluted with about 1% gallons of kerosene and stirred for 4 hours at 180- 200 F. The reaction mixture was dehydrated to 300 F., filtered with Super-Cel and vacuum topped to 350 F. at 0.5 mm. mercury absolute pressure to leave a product which analyzed as follows:

Percent barium 11.9 Percent sulfur 3.14 Base No. to pH 4 106.0

Example VI PREPARATION OF BASIC BARIUM PHENOL SULFIDE- SULFONIC ACID OIL REACTION PRODUCT CONCEN- TRATE 1000 grams of basic barium phenol sulfide as prepared in Example V was mixed with 3470 grams of acid oil, as prepared in Example I, at room temperature. A noticeable heat of reaction resulted which increased the temperature to 95 F. The mixture was slowly heated to 300 F. The amount of acid oil was calculated to be equivalent to one-half of the barium in the basic barium phenol sulfide. The product analyzed as follows:

Percent barium 2.62

Base No. to pH 4 14.8

Example VII PREPARATION OF BASIC BARIUM PHENOL SULFIDE- STEAMED OIL-Pass REACTION PRODUCT CONCEN- TRATE Percent barium 6.98 Percent phosphorus 1.33 Percent sulfur 2.42 Base No. to pH 4 45.6

Example VIII PREPARATION OF BASIC BARIUM PHENOL SULFIDE AND OIL-Fess REACTION PRODUCT CONCENTBATE 1000 grams of basic barium phenol sulfide as prepared in Example V, was mixed with 1490 grams of oil-P 5 reaction product, as prepared in Example 111, and slowly heated to 300 F. The amount of oil-P 8 reaction product was calculated to be equivalent to one-half of the barium content of the basic barium phenol sulfide. The product analyzed as follows:

Percent barium 4.8 Percent phosphorus 1.88 Percent sulfur 4.70 Base No. to pH 4 10.7

Example IX PREPARATION OF BASIC BARIUM PHE'NOL SULFIDE- DITHIOPHOSPHORIC ACID ESTER REACTION PROD- UCT CONCENTRATE 1000 grams of basic barium phenol sulfide, as prepared in Example V, was mixed with 313 grams of dithiophosphoric acid ester, as prepared in Example II. There was a noticeable heat of reaction. The mixture was slowly heated to 300 F. The amount of dithiophosphoric acid ester was calculated to be equivalent to onehalf of the barium in the basic barium phenol sulfide. The product analyzed as follows:

The benefits derived from the compositions of the present invention are illustrated by the following comparative oxygen absorption tests applied to mineral oil blends containing the compositions of the type illustrated in Examples VI through TX. The oxygen absorption tests were carried out at a temperature of 360 F. in the presence of a copper-lead catalyst on compositions blended to give a barium content of 0.52% by weight in a solvent-treated Mid-Continent neutral oil having a viscosity of about 160 SUS at F. As can be seen from the following table, a blend containing basic barium phenol sulfide absorbed 2200 cc. of oxygen in 232 minutes while a blend containing the new reaction product of basic barium phenol sulfide and dithiophosphoric acid ester as in Example IX, absorbed 1056 cc. in 300 minutes, or approx imately one-half as much oxygen in a time period of one-half again as long as the basic barium phenol sulfide. Improved results were also obtained with the other additives of this invention.

TABLE I Additive Amount of Concen- Additive Rate of Oxygen Additive trate Pre- Concen- Absorption per pared as in trate Wt. 100 grams of Example Percent in Blend No. Base 011 1 Base Oil 1 none 2,200 co. in 202 minutes. Basic Barium Phenol Sulfide V 4. 37 2,200 cc. in 232 minutes. Basic Barium Phenol Sulfide- VI 15.3 1,634 cc. in 300 Sultonic Acid Oil. minutes. Basic Barium Phenol Sulfidc- VII 7. 43 1,309 cc. in 300 Steamed P S -Hydr0carminutes.

on. Basic Barium Phenol Sulfide- VIII 10. 8 1,210 cc. in 300 P S -Hydrocarbon. minutes. Basic Barium Phenol Sulticle- IX 5. 74 1,056 cc. in 300 Dithiophosphoric Acid minutes. Ester.

1 The base oil is a solvent-treated Mid-Continent neutral of about 160 viscosity SU S at 100 F. with a viscosity index of 95. Each blend contained approximately 0.52% barium.

I claim:

1. A lubricating oil composition consisting essentially of a mineral lubricating oil and from 0.01 to 25.0 weight percent of a product obtained by reacting at a temperature from about room temperature to 500 F. an oilsoluble basic barium phenol sulfide with a quantity sufiicient theoretically to neutralize from one-half to all of the total barium content of the basic barium phenol sulfide of one oil-soluble material selected from the group consisting of petroleum sulfonic acid, dithiophosphoric acid diesters and phosphorus sulfide-hydrocarbon oil reaction products, and heating to remove water produced by said reacting.

2. The composition of claim 1 wherein said lubricating composition contains 0.5 to 10.0 weight percent of said reaction product.

3. The composition of claim 1 wherein quantities of said material selected from the group consisting of petroleum sulfonic acids, dithiophosphoric acid diesters and phosphorus sulfide-hydrocarbon oil reaction products equivalent to about half the barium in said basic barium phenol sulfide are reacted with said basic barium phenol sulfide.

4. The composition of claim 3 wherein said phosphorus sulfide-hydrocarbon oil product is prepared by reacting 7 to 17 weight percent of phosphorus pentasulfide with a mineral oil bright stock having a viscosity within the range of about to 300 SUS at 210 F. at a temperature between about 400 F. and 500 F. for a period of about 10 to 20 hours, and said dithiophosphoric acid diesters are prepared by reacting a mixture of C primary ,andC secondary alcohols with phosphorus pentasulfide;

5. A lubricating oil composition consisting essentially of a mineral lubricating oil and from about 0.01 to 25.0 weight percent of a product obtained by reacting at a temperature from about room temperature to 500 F. an oil-soluble basic barium phenol sulfide with a quantity suflicient theoretically ,to neutralize from one-half to all of the total barium content of the basic barium phenol sulfide of a dithiophosphoric acid diester and heating to remove water produced by said reacting.

6. The lubricant ofclaim 5 in which the diester is the product of the reaction under esterification conditions of a sulfide of phosphorus with an alcohol of 6 to 18 carbon atoms.

7. The lubricant of claim 5 in which the diester is the product of reaction of about 1 mol of P 8 with about 4 moles of mixed C -C alcohols.

UNITED STATES PATENTS Neely June 22,' Buckmanu July 19, Barton et al. Feb. 24, Lowe July 19, Rogers et al. Sept. 4, Kane et al. Feb; 12, Buck et a1. ..July 2,- Davidson et al. Oct. 1, Scott etal June 17, Moody et al. Aug. 26, Bowden et al. Mar. 5, Knapp et al. Ian. 24, 

1. A LUBRICATING OIL COMPOSITION CONSISTING ESSENTIALLY OF A MINERAL LUBRICATING OIL AND FROM 0.01 TO 25.0 WEIGHT PERCENT OF A PRODUCT OBTAINED BY REACTING AT A TEMPERATURE FROM ABOUT ROOM TEMPERATURE TO 500*F. AN OILSOLUBLE BASIC BARIUM PHENOL SULFIDE WITH A QUANTITY SUFFICIENT THEORETICALLY TO NEUTRALIZE FROM ONE-HALF TO ALL OF THE TOTAL BARIUM CONTENT OF THE BASIC BARIUM PHENOL SULFIDE OF ONE OIL-SOLUBLE MATERIAL SELECTED FROM THE GROUP CONSISTING OF PETROLEUM SULFONIC ACID, DITHIOPHOSPHORIC ACID DIESTERS AND PHOSPHORUS SULFIDE-HYDROCARBON OIL REACTION PRODUCTS, AND HEATING TO REMOVE WATER PRODUCED BY SAID REACTING. 